Fig. 4.
HX pulse-labeling results. Unfolded deuterated WT Cyt c (pDr 7.5, 4.2 M GdmCl, 10°C) was refolded by denaturant dilution (pH 6, 10°C, 0.23 M GdmCl, H2O). A kinetic intermediate, blocked by a histidine to heme misligation barrier, was H labeled in a 50-ms, high-pH pulse. The refolded native protein was analyzed by 2D NMR. The black dashed curves indicate the labeling expected for each amide in the absence of HX protection. The colored curves fit the labeling actually obtained within the intermediate alone (EX2 and EX1) after correction for extraneous effects (3, 16).